This invention relates to aqueous automatic dishwashing detergent compositions which have a yield value and are shear-thinning. Compositions of this general type are known. Examples of such compositions are disclosed in U.S. Pat. No. 4,116,851 to Rupe et al, issued Sep. 26, 1978; U.S. Pat. No. 4,431,559 to Ulrich, issued Feb. 14, 1984; U.S. Pat. No. 4,511,487 to Pruhs et al, issued Apr. 16, 1985; U.S. Pat. No. 4,512,908 to Heile, issued Apr. 23, 1985; Canadian Patent 1,031,229, Bush et al; European Patent Application 0130678, Heile, published Jan. 9, 1985; European Patent Application 0176163, Robinson, published Apr. 2, 1986; UK Patent Application 2,116,199A, Julemont et al, published Sep. 21, 1983; UK Patent Application 2,140,450A, Julemont et al, published Nov. 29, 1984; UK Patent Application 2,163,447A, Colarusso, published Feb. 26, 1986; and UK Patent Application 2,164,350A, Lai et al, published Mar. 19, 1986.
The state of the art liquid automatic dishwashing detergent compositions typically thickened with clay still suffer from phase separation upon storage under certain conditions. However, it has now been discovered that such compositions are improved by the utilization of certain-thickening and stabilizing agents. More specifically, automatic dishwashing detergent compositions comprising a polycarboxylate thickener and certain phosphate ester stabilizers have improved phase stability and cohesiveness.
The use of polyacrylic thickeners in liquid automatic dishwashing detergent compositions is known. See, for example, U.K. Patent Application 2,185,037, Dixit, published Jul. 8, 1987, which discloses liquid automatic dishwashing detergents which contain a long chain carboxylic or polycarboxylic acid as the thickener. Also, European Patent Application 0239379, Brumbaugh, published Sep. 9, 1987, teaches that polyacrylate is useful for water spot reduction in liquid automatic dishwashing detergent compositions. U.S. Pat. No. 4,226,736 to Bush et al, issued Oct. 7, 1980, teaches that a polymer of acrylic acid can be used as a thickener in liquid automatic dishwashing detergents instead of clay.
The use of phosphate esters, in general, in automatic dishwashing detergent compositions is also known. See, for example, U.K. Patent Application 2,116,199, Julemont et al, published Sep. 21, 1983, which teaches the use of an alkyl ester of phosphoric acid as a foam depressor.
The combination of polyacrylate thickeners and phosphate ester plus clay has also been taught in U.K. Patent Application 2,164,350, Lai et al, published Mar. 19, 1986. The polyacrylate thickeners taught to be useful have molecular weights of up to 500,000 (preferably up to 50,000). These compositions are said to be useful for protection of glazing on fine china.
It has now been found that if a polyacrylate thickener and certain phosphate esters are used together in the absence of clay in an automatic dishwashing detergent composition, enhanced phase stability and improved dispensing of the product from its container are achieved.